Eye registration and astigmatism alignment control systems and method

ABSTRACT

An orientation system for corrective eye surgery includes a camera for performing a first image mapping a patient&#39;s eye using a predetermined eye feature and software for processing the first image map to determine an edge location of the feature. A second image mapping is performed with the patient in a different position. The second image map is processed to locate the feature. In a second embodiment a pen is used to make two alignment marks on the eye. The eye is imaged with the patient in another position, and the image displayed. Software superimposes a graphical reticle onto the eye image, which is movable to align with the two alignment marks. In both cases software also calculates an orientational change to be applied to a corrective prescription for a surgical procedure to be performed on the eye with the patient in the second position.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from and incorporates by referencecommonly owned provisional applications Ser. No. 60/198,393, filed Apr.19, 2000, “Astigmatism Alignment Control Device and Method,” and Ser.No. 60/270,071, filed Feb. 20, 2001, “Eye Registration Apparatus andMethod.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems and methods for improvingobjective measurements preceding corrective eye surgery, and, moreparticularly, to such systems and methods for improving results ofcorrective laser surgery on the eye.

2. Description of Related Art

Laser-in-situ-keratomileusis (LASIK) is a common type of laser visioncorrection method. It has proven to be an extremely effective outpatientprocedure for a wide range of vision correction prescriptions. The useof an excimer laser allows for a high degree of precision andpredictability in shaping the cornea of the eye. Prior to the LASIKprocedure, measurements of the eye are made to determine the amount ofcorneal material to be removed from various locations on the cornealsurface so that the excimer laser can be calibrated and guided forproviding the corrective prescription previously determined by themeasurements. Refractive laser surgery for the correction of astigmatismtypically requires that a cylindrical or quasicylindrical ablationprofile be applied to the eye. The long axis of this profile must beproperly oriented on the eye in order to accurately correct the visualaberration.

An objective measurement of a patient's eye is typically made with thepatient typically sitting in an upright position while focusing on atarget image. A wavefront analyzer then objectively determines anappropriate wavefront correction for reshaping the cornea for theorientation of the eye being examined. The LASIK or PRK procedure isthen typically performed with the patient in a prone position with theeye looking upward.

It is well known that the eye undergoes movement within the socketcomprising translation and rotation (“cyclotortion”) as the patient ismoved from the upright measuring position to the prone surgery position.Techniques known in the art for accommodating this movement haveincluded marking the eye by cauterizing reference points on the eyeusing a cautery instrument (U.S. Pat. No. 4,476,862) or causticsubstance, a very uncomfortable procedure for the patient. It is alsoknown to mark a cornea using a plurality of blades (U.S. Pat. No.4,739,761). The injection of a dye or ink is also used to mark thereference locations to identify the orientation of the eye duringmeasurement, permitting a positioning of the corrective profile to thesame orientation prior to surgery. However, the time delay frommeasurement to surgery often causes the ink to run, affecting theaccuracy of an alignment. Making an impression on the eye (U.S. Pat. No.4,705,035) avoids the caustic effects of cauterizing and the runningeffect of the ink. However, the impression loses its definition quicklyrelative to the time period between the measurement and surgery.

For correction of astigmatism, it is known to mark the corneapreparatory to making the surgical incisions (U.S. Pat. No. 5,531,753).

Tracker systems used during the surgical procedure or simply forfollowing eye movement, while the patient is in a defined position, areknown to receive eye movement data from a mark on a cornea made using alaser beam prior to surgery (U.S. Pat. No. 4,848,340) or fromilluminating and capturing data on a feature in or on the eye, such as aretina or limbus, for example (U.S. Pat. Nos. 5,029,220; 5,098,426;5,196,873; 5,345,281; 5,485,404; 5,568,208; 5,620,436; 5,638,176;5,645,550; 5,865,832; 5,892,569; 5,923,399; 5,943,117; 5,966,197;6,000,799; 6,027,216).

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a systemand method for accurately orienting the eye for surgery.

It is a further object to provide such a system and method that orientsthe eye to the same orientation it had during an objective measurement.

It is another object to provide such a system and method that avoidsplacing the patient in an uncomfortable or harmful situation.

It is an additional object to provide such a system and method thatprovides an orientation correction algorithm to the software driving thecorrective surgical device.

It is yet a further object to provide such a system and method that canalign (register) pairs of eye images taken at different times.

These and other objects are achieved by the present invention, anorientation system for corrective eye surgery. A first embodiment of thesystem comprises means for performing a first image mapping an eye of apatient situated in a first position using a predetermined eye feature.Means are further provided for performing a second image mapping of theeye of the patient in a second position different from the firstposition using the predetermined eye feature. Means are also providedfor processing the first and the second image map to determine an edgelocation of the feature in two dimensions and to locate thepredetermined eye feature. Finally, software means are included forcalculating an orientational change to be applied to a correctiveprescription for a surgical procedure to be performed on the eye withthe patient in the second position. The procedure may comprise, forexample, a correction profile that had been determined with the patientin the first position with, for example, a wavefront analysis andconversion system for calculating an ablation profile for a cornea, suchas described in copending and co-owned application Ser. No. 09/566,668,the disclosure of which is hereby incorporated by reference.

The method of this first embodiment of the present invention is fororienting a corrective program for eye surgery and comprises the stepsof performing a first image mapping of an eye of a patient in a firstposition using a predetermined eye feature. The method also comprisesthe steps of performing a second image mapping of the eye of the patientin a second position different from the first position using the featureand processing the first and the second image map to determine an edgelocation of the feature in two dimensions and to locate the feature.Next an orientational change to be applied to a corrective prescriptionfor a surgical procedure to be performed on the eye with the patient inthe second position is calculated. The procedure comprises a correctionprofile determined with the patient in the first position.

Thus this aspect of the present invention provides a system and methodfor achieving a precise registration of the eye with a measurement ofthe movement of an eye feature. As a result, the prescriptionmeasurement for reshaping the cornea will account for the rotation andtranslation of the eye occurring between measurements made with thepatient in a sitting position and laser surgery with the patient in aprone position.

A second orientation system for eye surgery for correcting astigmatismcomprises means for making two alignment marks on an eye of a patientwith the patient in a first position. Means are also provided forimaging the eye with the patient in a second position that is differentfrom the first position. The system also comprises a computer that hasinput and output means. The input means are in electronic connectionwith the imaging means, and an operator input device is in electroniccommunication with the computer input means. Means are also incommunication with the computer input and output means for displayingthe eye image to an operator.

First software means are resident in the computer for superimposing agraphical reticle means onto the eye image on the displaying means andfor permitting the graphical reticle means to be moved by the operatorunder control of the operator input means. The reticle means comprise aline for aligning with the two alignment marks. Second software meansalso resident in the computer are for calculating an orientationalchange to be applied to a corrective surgical procedure to be performedon the eye with the patient in the second position. As above, theprocedure comprises a correction profile determined with the patient inthe first position.

The features that characterize the invention, both as to organizationand method of operation, together with further objects and advantagesthereof, will be better understood from the following description usedin conjunction with the accompanying drawing. It is to be expresslyunderstood that the drawing is for the purpose of illustration anddescription and is not intended as a definition of the limits of theinvention. These and other objects attained, and advantages offered, bythe present invention will become more fully apparent as the descriptionthat now follows is read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the system of the first embodiment ofthe present invention.

FIG. 2 is a block diagram of the data flow.

FIG. 3 is a view of the original image, before image processing, withfeature boxes around the features to be used as registration regions.

FIG. 4 is a view of a Gauss-filtered intensity profile with θ₁=0,showing the edge in an x direction.

FIG. 5 is a view of a Gauss-filtered intensity profile with θ₂=π/2,showing the edge in a y direction.

FIG. 6 is a view of a geometric average of FIGS. 4 and 5.

FIG. 7 is a view with threshold application.

FIG. 8 is a view of the image following application of the thinfunction.

FIG. 9 is a schematic diagram of the system of the second embodiment ofthe present invention.

FIG. 10 is a representation of an image of an eye as viewed on agraphical user interface in the second embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description of the preferred embodiments of the present invention willnow be presented with reference to FIGS. 1-10.

The System and Method of the First Embodiment

A schematic diagram of the system 10 of the first embodiment of theinvention is shown in FIG. 1, data flow in FIG. 2, and original andprocessed images in FIGS. 3-8. A section on the image processingalgorithms embodied herein follows the description of the system andmethod. In an exemplary embodiment of the system 10, a patient's eye 11is image mapped in a substantially upright position by capturing a firstvideo image 12 using a camera such as a charge-coupled-device (CCD)camera 13. Such an image 12 is illustrated in FIG. 3. The first image 12is stored in a database 14 in electronic communication with a computer15 and labeled as an original image from a first measurement.

Next an objective measurement is made on the eye 11 to determine adesired correction profile, using a measurement system 16 such as thatdisclosed in copending application 09/566,668, although this is notintended as a limitation.

Once the correction profile is determined, the patient is made ready forsurgery, and placed in the second position, which is typically prone.Alternatively, the first scan to determine the correction profile may bemade in a different location and at a time prior to the surgicalprocedure, the time interval being, for example, several weeks. Then asecond image map 17 is collected using a second camera 18, incommunication with a second system 38 for performing surgery, and thesedata are also stored in the database 14. In a preferred embodiment boththe first 13 and the second 18 cameras are adapted to collect colorimages, and these images are then converted using software resident onthe computer 15 to intensity profiles 19,20 as grey-scale images.Alternatively, color images may be used. It is useful to collect colorimages for viewing by the physician, since image mapping of the eye 11may made using preselected identifiable images such as blood vessels21,22 typically seen within the sclera 23. In a color image, the redcolor of the vessels 21,22 is clearly identifiable. Typically the secondimage map 17 is collected during setup prior to surgery using acorrection system such as is disclosed in application Ser. No.09/566,668, although this is not intended as a limitation. As the imagemaps 12,17 are typically collected with different cameras 13,18, thequalities of the images 12,17 are expected to be different, making theimage processing steps of great importance.

Next the intensity profile 19 of the first video image 12 is processedthrough weighting function such as a filter, in a preferred embodiment aGauss filter, although this is not intended as a limitation. This filteris for eliminating noise within the intensity profiles for definingimage edge locations in both an x and a y orientation to providetwo-dimensional information. The Gauss filter establishes a firstmodified intensity profile 24 with θ₁=0, as an example, as shown in FIG.4, an edge view in the x direction. The Gauss filter is again applied tothe intensity profiles to establish a second modified intensity profile25, with θ₂=π/2, as shown in FIG. 5, an edge view in a y direction.

A geometric average of the filtered x and y orientations is performedand processed to eliminate unwanted noise levels to form a firstfiltered intensity profile 26 for the first image 12, yielding a view asshown in FIG. 6, which has been calculated by taking the square root ofthe sum of the squares of the first 24 and the second 25 modifiedintensity profiles.

The above process is then repeated for the second image 17, to produce,from the second intensity profile 20, a third modified intensity profile27 from application of a Gauss filter with θ₃=0 and a fourth modifiedintensity profile 28, with θ₄=π/2, and geometric averaging to produce asecond filtered intensity profile 29.

Next an adaptive signal threshold is selected to reduce background noisefor the first 26 and the second 29 filtered intensity profiles,resulting in first 30 and second 31 thresholded images, as shown in FIG.7. The λ may be different for the two profiles 26,29; here λ=0.03.

The profiles 26,29 are then processed through a “thin function” toproduce a first 32 and a second 33 edge image (FIG. 8). This stepcompletes the image processing. Next the surgeon selects one or morefeatures in the eye 11, shown as a first 21 and a second 22 feature(here, blood vessels) in FIG. 3, and these are then used for correlatingbetween filtered images for the second (surgical) position of the eye 11with that of the first (measurement) position. Other features may alsobe used if sufficiently prominent blood vessels are not present. Theexcimer laser 36 coordinates are then reoriented to accommodate therotation and translation that took place when moving the patient from ameasurement instrument to the surgical device.

The operator proceeds to locate the limbus 34 using a graphical userinterface (GUI) while viewing the still image of the eye (FIG. 3). Byway of example, a reticle 37 is moved in position to coincide with thelimbus 34. The reticle size may be changed, including a diameter of acircular reticle, or optionally both minor and major radius of anelliptical reticle. The operator then selects a feature or features21,22 of the eye 11 to be used, and the above process is automaticallyperformed by the “push of a button,” which takes only seconds tocomplete in the exemplary embodiment.

Using the first 32 and second 33 edge images (FIG. 8), and knowing thecenter of the reticle 37 (circle or ellipse), the computer 15 determinescoordinates 38 for the selected features 21,22.

Image mapping within each feature box 21,22 is a process of using thetransformation described below. By way of example, the process fixes thefirst image 32 and varies the angle of orientation for second image 33.

The computer 15 overlays the first 32 and second 33 image with regard tocenter and compares each point within the feature box 21,22 and compareseach for different value of θ, while comparing each to determine maximummatching points. The computer 15 moves the center relation for each andseeks to improve its location (center a, b) and value for a θorientation. Each feature box or area (pixels within area) is processedbefore moving the center and is completed for every θ (typically−15°≦θ≦+15°, which will typically cover a patient's eye rotation whenmoving from an upright to a prone position. Completing the entireprocess takes less than 30 sec.

The treatment pattern, typically a laser shot pattern, is thus modifiedto account for eye rotation resulting from the patient's movement fromupright to prone position. In addition, an eye tracking feature of thesecond system 38 can account for eye movement during surgery.

By way of further example, code for carrying out the process steps toobtain the image of FIG. 8, and code for carrying out an exemplaryembodiment of the above for the steps including the feature coordinatedetermination through the processing of the feature boxes, were includedin provisional application No. 60/270,071, and are incorporated hereinby reference.

Another object of the present invention is to align (register) pairs ofeye images taken at different times. By way of example, images may betaken at:

1. An undilated pupil at centration time on wavefront system.

2. A dilated pupil at measurement time on wavefront system, usingmultiple measurements.

3. A dilated pupil on a surgical system following formation of the flap.

To align at least any two images from a mathematics point of view, it isassumed that there is enough information in each of the images to allowfor the precise computation of the translational and rotational offsetsbetween pairs of images such that any two images, by way of example, maybe overlaid with acceptably small errors. This condition satisfied, anoptimized linear transformation between these image pairs is determined.The transformation is described by three parameters: a translationvector r₀=(a,b) (a and b are the x and y coordinates of the translation,respectively) and a rotation angle θ, the transformation is uniquelydetermined by these three parameters.

Image Processing

The Gauss filter is used to eliminate the noise of both images and isdefined as:

G(x,y,σ ₁,σ₂)=g(u(x,y),σ₁)·g′ _(v)(v(x,y),σ₂)   1

where $\begin{matrix}{{{{g\left( {u,\sigma} \right)} = {\frac{1}{\sqrt{2{\pi\sigma}^{2}}}{\exp \left( {- \frac{u^{2}}{2\sigma}} \right)}}};}{{g_{v}^{\prime}\left( {v,\sigma} \right)} = {{- \frac{v}{\sigma}}{g\left( {v,\sigma} \right)}}}} & (2)\end{matrix}$

and

u(x,y)=cos θ·x−sin θ·y  3

v(x,y)=sin θ·x+cos θ·y  4

is the rotation of the point (x, y) and θ is the angle of rotation. Hereθ is set to be either 0 or π/2, which means the filter will eliminatethe noise either in the x direction or the y direction. The standarddeviation (σ) determines the shape of the filter.

Let Im(x,y) represent the image data function. Applying the Gauss filterto the image function is equivalent to making the convolution of thesetwo functions.

NewIm(x,y)=Im(x,y)*G(x,y,σ ₁,σ₂)  5

Next the threshold ξ is computed.

ξ=λ·max|NewIm(x,y)|+(1−λ)·min|NewIm(x,y)|  6

where 0<λ<1. The threshold to the new image file is applied as$\begin{matrix}{{{Im}\quad {N\left( {x,y} \right)}} = \left\{ \begin{matrix}{{{New}\quad {{Im}\left( {x,y} \right)}}} & {{{if}\quad {{{New}\quad {Im}\quad \left( {x,y} \right)}}} > \xi} \\\xi & {otherwise}\end{matrix} \right.} & 7\end{matrix}$

A bilinear interpolation method is used to determine the edge point, thefollowing comprising a thin function:

P=(1−α)[(1−β)P ₀ +βP ₂]+α[(1−β)P ₁ +βP ₃]  8

where gradient vector

gradient of Im(x,y)=(α,β)  9

and P_(i) are points in a neighborhood of (x,y).

Image Mapping

After processing both images, the best parameters in this lineartransformation should be found. The “best” means that, in a givenparameter space, it is desired to find a point (parameters) in thatspace, such that under these parameters the linear transformationminimizes the error between those pairs of images.

The linear transformation is defined as: $\begin{matrix}{\begin{pmatrix}x^{\prime} \\y^{\prime}\end{pmatrix} = {{\begin{pmatrix}{\cos \quad \theta} & {{- \sin}\quad \theta} \\{\sin \quad \theta} & {\cos \quad \theta}\end{pmatrix}\begin{pmatrix}{x - {center}_{x}} \\{y - {center}_{y}}\end{pmatrix}} + \begin{pmatrix}a \\b\end{pmatrix}}} & 10\end{matrix}$

The criterion to find the best transform parameters is to minimize theerror: $\begin{matrix}{\min\limits_{{({a,b,\theta})}ɛ\quad D}{\sum\limits_{({x,y})}{{{{Im}\quad {N_{prior}\left( {x,y} \right)}} - {{Im}\quad {N_{post}\left( {x^{\prime},y^{\prime}} \right)}}}}}} & 11\end{matrix}$

The pair (center_(x), center_(y)) is the coordinate of the center pointof the limbus from one image.

D={(a,b,θ)|a ₁ <a<a ₂ , b ₁ <b<b ₂, θ₁<θ<θ₂}  12

is the parameter (searching) space. The problem is to determine the(center_(x), center_(y)) and the searching space {a₁,a₂,b₁,b₂,θ₁,θ₂}.The limbus is manually located in this embodiment on both images toobtain the center coordinate (center_(x), center_(y)) from themeasurement system, and the center coordinate (center_(xx), center_(yy))from the surgical system. Then the search region is defined as

a ₁=center_(xx) −k, a ₂=center_(xx) +k  13

b ₁=center_(yy) −k, b ₂=center_(yy) +k  14

where k is a integer. The searching resolution is Δθ=0.5°, and thesearch range is ±15°; so θ₁=−15°, θ₂=+15°. The summation Σ is taken overa reference area (x,y) ε Ω. The reference area is manually located tosatisfy the assumption mentioned above.

The System and Method of the Second Embodiment

The second embodiment of the present invention includes an orientationsystem 40 for eye surgery for correcting at least astigmatism, which isshown schematically in FIG. 9. A means for making two alignment marks41,42 on an eye 43 of a patient with the patient in a first position maycomprise, for example, an ink pen 44, although this is not intended as alimitation, and alternative marking means known in the art may also becontemplated for use. In current use, the first position typicallycomprises a seated upright position. In a preferred embodiment, themarks 41,42 are made at the “3 o'clock” and “9 o'clock” positions to theeye's sclera 45 just outside the limbal margin 46. In other words, themarks 41,42 are made at approximately the π/2 and 3π/2 radial positionsrelative to the limbus 46, with a 0 radial position comprising a toppoint of the limbus 46. Thus the marks 41,42 are made substantiallycollinear with a diameter of the limbus 46.

A camera, preferably a color video camera 47, is provided for imagingthe eye with the patient in a second position different from the firstposition. Typically the second position comprises a prone position.

The system 40 also comprises a computer 48 that has input and outputmeans. One input 49 is in electronic connection with the camera 47.Means are also in communication with the computer's input and outputmeans for displaying the eye image to an operator (FIG. 9). Such adisplay means may comprise, for example, a color video display monitor50. An operator input device, which may comprise, for example, a mouse51, is also in electronic communication with another input 52 to thecomputer 48. Alternatively, other operator input devices may becontemplated; for example, the monitor 50 may comprise a touch screen.

In a preferred embodiment, the corrective system 53 to be used inperforming surgery, for example, laser ablation surgery on the cornea,comprises an eye tracker 54 as discussed above. In this embodiment, themonitor 50 displays both a tracked eye image 55 and an untracked eyeimage 56 (FIG. 10).

A first software routine 57 is resident in the computer 48 for routingthe eye images to the monitor 50 and also for superimposing a graphicalreticle 58 onto the tracked eye image 55. The first software 57 furtherpermits the reticle 58 to be moved by the operator under control of themouse 51. The reticle 58 comprises a circle 59 for superimposing on theeye's limbus 46 and a cross-hair including a pair of perpendicular lines60,61, both of which are substantially diametric with the circle 59.Typically the generally horizontal line 60 is used to align with thealignment marks 41,42 on the eye 43. In a color system, the reticle 58comprises a color for contrasting with the eye 43, such as, but notlimited to, yellow.

The monitor 50 preferably comprises a graphical user interface 62 thathas an interactive control sector 63 thereon. As shown in the exemplaryscreen of FIG. 10, the control sector 63 comprises a plurality ofcontrol sectors, in the form of “buttons,” the activation of which movesthe reticle 58 in a desired direction. Here the buttons comprise two forhorizontal movement, “left” 64 and “right” 65, two for verticalmovement, “up” 66 and “down” 67, and two for rotation, counterclockwise68 and clockwise 69. Clicking on these buttons 64-69 with the mouse 51causes motion of the reticle 58 on the interface 62 in the indicateddirection, as mediated by the first software 57 (see rotated reticle inFIG. 9).

In addition, a button 71 performs recentering of the lines 60,61 overthe cornea.

A second software routine 71 is also resident in the computer 48 forcalculating an orientational change to be applied to a correctivesurgical procedure. The procedure, also resident in the computer 48, isto be performed on the eye 43 with the patient in the second position.Such a procedure may comprise, for example, an ablation correctionprofile that had been determined by a measurement system 71 inelectronic communication with the computer 48, with the patient in thefirst position.

It will be understood based on the teachings of the present inventionthat in addition to images viewed on the surface of the eye, theposition of the retina and any movement thereof may be determined usingthe above methods to view images on the retina. In the same way that thescleral blood vessels are stationary relative to the corneal surface,the retinal blood vessels are also stationary relative to the cornea. Byway of example, the video camera may be replaced by a scanning laserophthalmoscope, as disclosed in U.S. Pat. No. 6,186,628 to Van de Velde,which disclosure is hereby incorporated by reference; a retinal nervefiber layer analyzer, as disclosed in U.S. Pat. No. 5,303,709 to Dreheret al., which disclosure is hereby incorporated by reference; or afundus camera to provide images of blood vessel patterns that can beused in the same manner as scleral blood vessels as herein described.

In the foregoing description, certain terms have been used for brevity,clarity, and understanding, but no unnecessary limitations are to beimplied therefrom beyond the requirements of the prior art, because suchwords are used for description purposes herein and are intended to bebroadly construed. Moreover, the embodiments of the apparatusillustrated and described herein are by way of example, and the scope ofthe invention is not limited to the exact details of construction.

Having now described the invention, the construction, the operation anduse of preferred embodiment thereof, and the advantageous new and usefulresults obtained thereby, the new and useful constructions, andreasonable mechanical equivalents thereof obvious to those skilled inthe art, are set forth in the appended claims.

What is claimed is:
 1. An orientation system for eye surgery forcorrecting astigmatism comprising: means for making two alignment markson an eye of a patient, the patient in a first position; means forimaging the eye with the patient in a second position different from thefirst position; a computer having input and output means, the inputmeans in electronic connection with the imaging means; an operator inputdevice in electronic communication with the computer input means; meansin communication with the computer input and output means for displayingthe eye image to an operator; first software means resident in thecomputer for superimposing a graphical reticle means onto the eye imageon the displaying means and for permitting the graphical reticle meansto be moved by the operator under control of the operator input means,the reticle means comprising a line for aligning with the two alignmentmarks; and second software means resident in the computer forcalculating an orientational change to be applied to a correctivesurgical procedure to be performed on the eye with the patient in thesecond position, the procedure comprising a correction profiledetermined with the patient in the first position.
 2. The system recitedin claim 1, wherein the mark making means comprises an ink pen.
 3. Thesystem recited in claim 1, wherein the two alignment marks are made atapproximately π/2 and 3π/2 radial positions relative to a limbus of theeye, with a 0 radial position comprising a top point of the limbus. 4.The system recited in claim 3, wherein the two alignment marks are madeadjacent a limbus of the eye.
 5. The system recited in claim 1, whereinthe imaging means comprises a video camera.
 6. The system recited inclaim 5, wherein the camera comprises a color video camera.
 7. Thesystem recited in claim 1, wherein the displaying means comprises avideo display monitor.
 8. The system recited in claim 7, wherein thevideo display monitor comprises a color display monitor and the reticlemeans comprises a color for contrasting with the eye.
 9. The systemrecited in claim 1, wherein: the two alignment marks are madesubstantially collinear with a diameter of a limbus of the eye; thereticle means further comprises a circle for superimposing on thelimbus; and the line is substantially diametric with the circle.
 10. Thesystem recited in claim 9, wherein the line comprises a first line, andthe reticle means further comprises a second line substantiallyperpendicular with the first line.
 11. The system recited in claim 1,wherein the display means comprises a graphical user interface having aninteractive control sector thereon, an activation of the sector usingthe user input means causing a movement of the reticle means on theinterface.
 12. The system recited in claim 11, wherein the controlsector comprises a plurality of control sectors comprising two controlsectors for horizontal movement, two control sectors for verticalmovement, and two control sectors for rotation.
 13. The system recitedin claim 12, wherein the control sectors further comprise a controlsector for centering the reticle means over a cornea of the eye.
 14. Thesystem recited in claim 1, further comprising means for tracking eyemovement, and wherein the displaying means further comprises means fordisplaying a tracked eye image.
 15. A method for orienting a correctiveprogram for eye surgery comprising the steps of: making two alignmentmarks on an eye of a patient, the patient in a first position; imagingthe eye with the patient in a second position different from the firstposition; displaying the eye image to an operator; electronicallysuperimposing a graphical reticle means onto the eye image, the reticlemeans comprising a line; moving the graphical reticle means to align theline with the two alignment marks; and automatically computing anorientational change to be applied to a corrective surgical procedure tobe performed on the eye with the patient in the second position, theprocedure comprising a correction profile determined with the patient inthe first position.
 16. The method recited in claim 15, wherein the markmaking step comprises marking with an ink pen.
 17. The method recited inclaim 15, wherein the two alignment marks are made at approximately π/2and 3π/2 radial positions relative to a limbus of the eye, with a 0radial position comprising a top point of the limbus.
 18. The methodrecited in claim 17, wherein the two alignment marks are made adjacent alimbus of the eye.
 19. The method recited in claim 15, wherein theimaging step comprises using a video camera to image the eye.
 20. Themethod recited in claim 19, wherein the camera comprises a color videocamera.
 21. The method recited in claim 15, wherein the displaying stepcomprises using a video display monitor to display the eye image. 22.The method recited in claim 21, wherein the video display monitorcomprises a color display monitor and the reticle means comprises acolor for contrasting with the eye.
 23. The method recited in claim 15,wherein: the two alignment marks are made substantially collinear with adiameter of a limbus of the eye; the reticle means further comprises acircle for superimposing on the limbus; and the line is substantiallydiametric with the circle.
 24. The method recited in claim 15, whereinthe line comprises a first line, and the reticle means further comprisesa second line substantially perpendicular with the first line.
 25. Themethod recited in claim 15, wherein the displaying step comprises usinga graphical user interface having an interactive control sector thereonto display the eye, the sector activatable to cause a movement of thereticle means on the interface.
 26. The method recited in claim 25,wherein the control sector comprises a plurality of control sectorscomprising two control sectors for horizontal movement, two controlsectors for vertical movement, and two control sectors for rotation. 27.The method recited in claim 26, wherein the control sectors furthercomprise a control sector for centering the reticle means over a corneaof the eye.
 28. The method recited in claim 15, further comprising thestep of tracking eye movement, and wherein the displaying step furthercomprises displaying a tracked eye image.